The following discussion of the background art is intended to facilitate an understanding of the present invention only. The discussion is not an acknowledgement or admission that any of the material referred to is or was part of the common general knowledge as at the priority date of the application.
For the LPI process it is necessary to deliver liquefied gaseous fuel to a fuel injector in the liquid phase. The requirement to maintain the liquid phase of the liquefied gaseous fuel necessitates that the fuel be maintained under pressure.
During the delivery process there is a phase change at the outlet of the injector, which can lead to rapid cooling and, consequently, formation of ice on the tip of the injector nozzle. The formation of ice on the injector nozzle is disadvantageous as it can lead to deterioration in the performance of the nozzle.
There have been various strategies proposed to address the issue of icing of an injector nozzle.
For indirect injection applications, one known strategy involves configuring the fuel injector as an injector body and a nozzle portion, with the nozzle portion providing an extension from the nozzle body to terminate at the nozzle tip. The extension is adapted to be received in an injection socket which is typically an intake manifold injector bore. The extension defines a delivery path which extends from a receiving chamber within the injector body and along which the gaseous fuel can be conveyed to the nozzle tip for delivery into the injection socket.
The extension comprises an inner tube defining the fuel delivery path terminating at the nozzle tip and a casing surrounding the inner tube, the casing presenting an end face at the tip of the nozzle portion.
Typically, the inner tube terminates at the end face of the nozzle portion so as to be flush therewith. However, some variation can occur due to imprecision in the assembly process in relation to positioning of the end of the inner tube with respect to the end of the nozzle portion, with the result that the inner tube can often protrude beyond, or terminate inwardly of, the end face of the nozzle. Unexpected or unwanted protrusion of the inner tube beyond the end face can be undesirable in certain circumstances. It is undesirable if the protrusion is to such an extent that the exposed section of the inner tube is chilled during the delivery process so that a detrimental build-up of ice develops on the exposed surface of the tube. Further, it is undesirable if the protrusion is to such an extent as to affect alignment of the protruding portion of the inner tube and thereby affect the direction of delivery of the gaseous fuel. Similarly, termination of the inner tube inwardly of the end face may expose the surrounding region of the nozzle portion to fluid flow in the fuel delivery process. This may obstruct the delivery of gaseous fuel and also chill the surrounding region of the nozzle portion, causing detrimental ice formation.
The casing about the inner tube is adapted to provide thermal insulation to prevent heat transfer during passage of the liquefied gaseous fuel to the outlet. Further, the extension is adapted to collect heat from the engine, thereby contributing to a reduction in thermal losses during passage of the liquefied gaseous fuel to the outlet. Additionally, heat so collected may assist in the reduction of icing at the nozzle outlet.
Notwithstanding these strategies, icing at the nozzle outlet can still occur.
It would be advantageous to provide an arrangement which overcomes, or at least ameliorates, the potential for icing at the nozzle tip while also avoiding the need for precision in the location of the end of the inner tube with respect to the end of the nozzle portion in order for effective delivery of the injected gaseous fuel.